ken scharf wrote:
julian814 wrote:
Today, I am reminded that Google is my friend. After much digging and
prodding, I found what I was looking for. It seems the National SW-54
receiver is as close to what I want as possible without me having to do
math. It dates back to the 50's, uses tubes, (in fact, I already have
three of the five in it) covers a good amount of the SW band, and will
drive either my 2000 ohm headphones or a 4" speaker. BAMA had the
manual, but it wouldn't give it up, so I had to go to the mirror site
to get it. Everything I need is in it - schematics, parts list,
pictures of the assembled receiver. Not exactly the ideal radio for a
first try, but nothing good ever came easy, did it? ;-)

Thanks again to everyone who offered advice and suggestions. I'll be
sure to post when I have it together and let everyone know how I made
out.

Time to scrounge for parts.


Ralph

OPPS, I confused the sw-54 with the sw3-5 series.
This one is a "modern" superhet. Do you have the IF transformers, band
switch and coils?

I have a complete band switch and coil assembly from an old Lafayette
short wave receiver. It is a 4 band assembly with rf, osc, and mixer
coils intended for use with a 3 gang 365pf/section tuning capacitor.
I was thinking of using this in some project (that never happened), but
it sounds like just what you want. The coils have slug tuned tracking
adjustments, and the oscillator and mixer coils also have trimmer
capacitor tracking too.

If you can use this let me know.

PS, if you use this you'll have to change the tube lineup to take full
advantage of all the coils. Replace the 50c5 with a 35c5 and add
another 12ba6 for an rf amplifier. Actually you should use all 6v tubes
and a power transformer. Those AC/DC sets are "undertakers labs"
approved shock hazards. An "isolation transformer will fix that of course."

The schematic of the receiver the coil switch assembly came from is here
http://bama.edebris.com/manuals/lafayett/ha700/

I'm starting to think I should just settle for that crystal shortwave
set I found on the Antique Radio website. Less headaches.

No idea where to get the coils for the SW-54, so I guess that's out.
Besides, since this is my first real attempt at making a radio, I
should probably go for something simpler.

Going back to Google to see if I can find more on some of the tubes I
have. I keep thinking I should be able to make a regenerative receiver
with some amplification with the two 12AV6 tubes I have.

Ralph

Managed to find a regenerative receiver based on the 12AT7 tube. I've
been told I can substitute one of my 12AV6 tubes without a problem, so
that looks promising.

I have some twin triode tubes, as well. (6FQ7, 6BZ7 and 4BC8) I've been
wondering if I couldn't make some one tube receivers with them. (Use
one triode for regeneration, the other an amplifier.) As for the rest
of the tubes I have, I'd be willing to sell or swap for parts I'll
need.

Ralph

julian814 wrote:
Managed to find a regenerative receiver based on the 12AT7 tube. I've
been told I can substitute one of my 12AV6 tubes without a problem, so
that looks promising.

I have some twin triode tubes, as well. (6FQ7, 6BZ7 and 4BC8) I've been
wondering if I couldn't make some one tube receivers with them. (Use
one triode for regeneration, the other an amplifier.) As for the rest
of the tubes I have, I'd be willing to sell or swap for parts I'll
need.

Ralph

http://www.lindsaybks.com/bks/twin/index.html

ken scharf wrote:
julian814 wrote:
Managed to find a regenerative receiver based on the 12AT7 tube. I've
been told I can substitute one of my 12AV6 tubes without a problem, so
that looks promising.

I have some twin triode tubes, as well. (6FQ7, 6BZ7 and 4BC8) I've been
wondering if I couldn't make some one tube receivers with them. (Use
one triode for regeneration, the other an amplifier.) As for the rest
of the tubes I have, I'd be willing to sell or swap for parts I'll
need.

Ralph

http://www.lindsaybks.com/bks/twin/index.html

I think this link might be more helpful and cheaper.

http://dzabcik.home.texas.net/doerle.html

Of course, it doesn't have Lindsay's notes on using newer tubes.


Ralph

julian814 wrote:
ken scharf wrote:
julian814 wrote:
Managed to find a regenerative receiver based on the 12AT7 tube. I've
been told I can substitute one of my 12AV6 tubes without a problem, so
that looks promising.

I have some twin triode tubes, as well. (6FQ7, 6BZ7 and 4BC8) I've been
wondering if I couldn't make some one tube receivers with them. (Use
one triode for regeneration, the other an amplifier.) As for the rest
of the tubes I have, I'd be willing to sell or swap for parts I'll
need.

Ralph

http://www.lindsaybks.com/bks/twin/index.html

I think this link might be more helpful and cheaper.

http://dzabcik.home.texas.net/doerle.html

Of course, it doesn't have Lindsay's notes on using newer tubes.


Ralph

Well If you are familiar with the book you know he showed a version
using a 6sl7gt tube. The 12at7 triode is identical to one half of the
6sl7 (except for heater voltage) so you can use a pair of these tubes in
the same circuit.

I built the #19 version, which worked ok but this tube is VERY
microphonic. I suspect the 12at7 will not have that problem.

Another interesting version of the theme was a single tube regen that
appeared in 'poptronics. It used a 6af11 compactron. This tube has two
triodes and a power pentode, so it will drive a speaker.

Also the current issue of QST shows a very simple untuned rf amplifier
that can be added to any tube type regen receiver. It uses only 7 parts
(a resister, 3 caps, 1 diode, an rf choke, and a transistor). The rf
choke and one of the caps can be eliminated if you directly couple the
output of the rf amp to the receiver via a link added to the input coil.
One of the caps and the diode are used to steal 9v dc from the 6.3v
heater supply. I would recommend adding this as it makes the receiver
easier to tune by isolating it from the antenna.